Question

In the reaction, $A\to$ Products, when the concentration of $A$ was reduced from $2.4\times {10}^{-2}M$ to $1.2\times {10}^{-2}M$, the rate decreased $8$ times at the same temperature. The order of the reaction is:

• A. $0$
• B. $1$
• C. $2$
• D. $3$
• E. $0.5$

Answer 1

Answer: (D)

$3$

Change in concentration $=2.4\times {10}^{-2}-1.2\times {10}^{-2}=1.2\times {10}^{-2}M$

Rate change $=8$ times

$\because$ Rate $\propto {\left(Changeinconcentration\right)}^n$

$\therefore 8r\propto {(1.2\times {10}^{-2})}^n$

$2^{3}r\propto {(1.2\times {10}^{-2})}^n$

On comparing, the powers of rate and change in concentration,
$n=3$

Thus, the order of reaction $=3$

Hence, option D is correct.